Study On Bioelectrochemical Sensing Of Composites Based On Nitrogen Doped Graphene And Metal Sulfide

In recent years,the non-enzyme modified electrode sensor has become a new technology which combines multi-disciplines with interpenetration in bio-electrochemical sensors because of its low cost,good selectivity,high sensitivity,wide concentration range,etc.Glucose,hydrogen peroxide and nitrite are important analytes in the field of medicine and food.Therefore,it is inevitable to create a novel nano-material on new electrochemical non-enzyme biosensors for rapid and accurate detection.Of these substances graphene has been widely studied in various fields due to its excellent properties,such as large specific surface area,high thermal conductivity,fast carrier mobility etc.since it was first deposited by mechanical exfoliation in 2004.However,the application of graphene is limited in the field of electrochemistry owing to its low reactivity.In order to improve its electrical properties,the chemical doping has become an effective inorganic chemistry technology.Nitrogen doped graphene has been further studied because the strong betatopic ability of nitrogen atoms can produce defects around the carbon atoms and hence improve the electrocatalytic activity of graphene.The propose of this work is to synthesize a series of nanocomposites on the basis of sulfur metal nanomaterials functionalized nitrogen-doped graphene.Moreover,these nanocomposites can exhibit high electrocatalytic activity for glucose,hydrogen peroxide and nitrite attributing to the synergistic effect of nitrogen-doped graphene and sulfur metal nanomaterials.The main contents of the paper include the following four aspects:1.The composites formed by N-graphene and CoS₂ nanomaterials were explored and synthesized by solvothermal method,and then the non-enzyme glucose sensor was studied by CoS₂/N-graphene nanocomposite material modified electrode.The results show that CoS₂/N-graphene nanocomposite modified electrode exhibits the best electrocatalytic effect towards the oxidation of glucose,compared with bare glassy carbon electrode,N-graphene and single CoS₂ nanomaterial modified electrode.The oxidation peak current is linear with the concentration of glucose in the range of 4?M⁵.536 m M,with the sensitivity of 421.75 ?A·m M-1·cm^-2,and the detection limit of1.3 ?M.The enhanced electrochemical performance of CoS₂/N-graphene is contributed to the synergic effect of N-graphene and CoS₂.Moreover,the sensor based on CoS₂/N-graphene composites exhibit good selectivity,stability and repeatability.These superior properties indicate that the nanocomposites are expected to develop into an electrochemical sensor for online detection of glucose.2.The sponge-like Co₄S₃ nanomaterials with small particles were prepared and combined with N-graphene to form nanocomposites.Then the electrochemical response of H2O2 molecules on this modified electrode was studied.The results showed that Co₄S₃/N-graphene composite electrode has the strongest electrocatalytic effect on H2O2 compared with the bare glassy carbon electrode and the single Co₄S₃ material modified electrode.Under the optimized conditions,the reduction peak current was linear with the concentration of H2O2 in the range of 1 ?M².18 m M.The low detection limit of the sensor was estimated to be 0.29 ?M?S/N=3?with the high sensitivity of 65.63 ?A/m M.Moreover,the proposed electrochemical H2O2 sensor exhibited a rapid response to H2O2 within 2 s.3.In the experiment,Ni S/N-graphene composites were synthesized by simple solvothermal method.And then non-enzymed electrochemical glucose sensor was constructed,the glucose could be detected by nonenzyme method in an environmentally friendly manner.An excellent electrocatalytic oxidation activity toward glucose of Ni S/N-graphene was demonstrated owing to the large surface area and fast rate charge tranfer.As a consequence,the Ni S/N-graphene based sensor exhibite a wide linear range?5 ?M ¹.475 m M?,a low detection limit?1.7?M,S/N=3?,a high sensitivity?60.51?A·m M-1?,along with the good selectivity.This can provide a promising platform for electrochemical sensor designs.4.Cu S nanomaterials and Cu S/N-graphene nanocomposites were synthesized by using ethanol as solvent,and their phase analysis,morphological analysis and elemental analysis were carried out necessarily.The electrocatalytic effect of Cu S/N-graphene nanocomposites on nitrite was investigated by Cyclic voltammetry.The experimental results show that the oxidation effect of Cu S/N-graphene nanocomposites on nitrite is stronger than that of Cu S nanomaterials,the oxidation peak current is higher and the oxidation peak potential is significantly negative shift.After optimizing the experimental conditions,it was found that the nitrite concentration had a good linear relationship with the oxidation peak current between 1 ?M and 14.014 m M,and the detection limit was 0.33 ?M.The composite electrode was successfully used to detect nitrite in the actual sample,which is not interfered by common coexisting components and had good reproducibility and long electrode stability.